What Size Vanity Light for 48-Inch Vanity? | Sizing That Looks Right

For a 48-inch vanity, the best vanity light width is roughly 36 inches — about 75 percent of the mirror’s width.

Choosing a light for a 48-inch vanity isn’t about the vanity at all. It’s about the mirror sitting above it. Match the fixture to the mirror, not the countertop, and the whole setup looks intentional. A fixture sized to about 75 percent of the mirror width — usually landing in the 28–40 inch range — casts balanced light across your face without spilling past the mirror’s edges.

Here’s what determines the right size, how placement changes the math, and where double-sink layouts need a different approach.

Measure the Mirror, Not the Vanity

The most consistent sizing rule for vanity lighting is simple: pick a fixture that spans about 75 percent of the mirror’s width. For a 48-inch vanity with a 48-inch mirror, that works out to roughly 36 inches — and most guides agree on a 24–36 inch range for this vanity size. Some sources stretch that to 30–36 inches, while broader manufacturer guidance allows 28–40 inches for a 48-inch vanity with a 40–44 inch mirror.

Three common mistakes throw this off:

• Buying a fixture wider than the mirror — it looks oversized and casts light where you can’t see it.
• Choosing based on vanity width alone instead of mirror width, which leads to a fixture that overhangs a narrower mirror.
• Ignoring whether the layout is single-sink or double-sink, which changes the whole approach.

What Size Fits a Single-Sink 48-Inch Vanity?

For a standard single-sink setup, a bar light in the 30–36 inch range is the sweet spot. If your mirror is the full 48 inches wide, a 36-inch fixture keeps the proportions balanced while staying a few inches inside the mirror’s edges on each side.

The catch: your mirror may not be 48 inches. Many vanities ship with narrower mirrors, and that changes everything. A 48-inch vanity with a 36-inch mirror needs a smaller fixture — think 24–30 inches — because the light should never extend beyond the mirror. Measure the actual mirror width before you shop, then multiply by 0.75 to find your target fixture size.

Mount the fixture so its center sits 75 to 82 inches from the floor. That places the light at a flattering height for most people and keeps it out of the mirror’s reflection zone.

Double-Sink Vanities: One Bar or Two Fixtures?

For a 48-inch vanity with two sinks — or any vanity 48 inches and wider — you have two solid options. One long fixture spanning 36–48 inches works well, or two smaller fixtures mounted one above each sink. The two-fixture route gives each sink its own even task lighting, which many homeowners prefer for grooming tasks like shaving or makeup application.

The same 75-percent rule applies per mirror: if each sink has its own mirror, size each fixture to about 75 percent of that individual mirror’s width. Two 18–24 inch fixtures above twin mirrors often look more balanced than one wide bar fighting two mirror edges.

Some designers skip the bar light entirely for larger vanities and mount two sconces on either side of the mirror instead. That’s a viable look for a 48-inch double-sink layout, but sconces alone rarely provide enough downward light for detailed tasks — pairing them with overhead or recessed lighting is the safer bet.

Fixture Width vs. Mirror Width: Quick Reference

This table condenses the sizing math for common mirror widths found on 48-inch vanities.

One more variable worth checking: your bathroom’s electrical setup. Vanity lighting in a bathroom should be rated for damp locations where moisture is a factor, and the specific model’s installation suitability depends on your wiring and wall layout. Product spec pages note dimensions and ratings — read those before you buy.

If you’re leaning toward a warmer, classic finish for your 48-inch vanity, our tested picks for the best antique brass vanity lights cover fixtures that pair well with this mirror-width math.